The table that show the ethanol % only state a minimium amount of ethanol specified.
Ethanal does have a faster burn rate than gas. Heres the kicker about e85, the more gas it has in it the more timing you need to run. I had a bunch of local cars that when they switched to the winter blend(more gas, less ethanol) had to be retuned, they all took about 5 degrees more timing to make the same power as they did before. I have dyno sheets and corresponding track slips to back that statement up.
I do agree a small swing in ethanol % doesnt make much of a difference, but that isnt typically the case. I've seen a afr swing from tank to tank of e85 be as high as 3 pts. I've seen e85 have 98% ethanol, and i've seen it have 74%.
The e10 users are fine, because the % of change is fairly small, and you need roughly 30% more fuel for ethanol so that 10% swing, really is smaller than that. Typically gas stations run the max ethanol allowed, its cheaper than gas so the more ethanol they use the more money they make.